BACKGROUND: Ambu-bags and portable ventilators can provide intubated patients with ventilation during intrahospital transport, where it is desirable to maintain normocarbia. This study was designed to compare the amount of variation in ventilation that occur during the intrahospital transport of neurosurgical patients ventilated either manually or with a portable ventilator. METHODS: 40 patients were randomized to receive either manual ventilation (Group A, n = 20) during transport or ventilation by a portable ventilator (Group P, n = 20) during the immediate postoperative period. In group A, an adult laerdal resuscitator bag with a reservoir bag (2,600 ml) was used and oxygen (15 L/min) was supplied from a portable oxygen tank. In group P, a portable ventilator was set to controlled mechanical ventilation or synchronized intermittent mandatory ventilation mode, 8.5-10 ml/kg of tidal volume, 1:2 of inspiratory to expiratory ratio, and 100% oxygen concentration. Respiratory rates were adjusted to maintain normocarbia. Hemodynamic parameters were recorded before and during transport. Arterial blood gas levels were also obtained before and during transport. RESULTS: PaCO2 during transport was significantly lower in Group A than in Group P (P < 0.05). Manually ventilated patients showed greater deviations from normocarbia (35-45 mmHg) than mechanically ventilated patients (P < 0.01). PaO2 during transport was no different in the two groups. Blood pressure and heart rates during transport increased significantly in both groups versus before transport (P < 0.01). CONCLUSIONS: The use of a portable ventilator can effectively maintain normocarbia and produce the stable ventilatory pattern during the intrahospital transport of neurosurgical patients during immediate postoperative period.